Lubricant for high bearing pressures



Patented May 28, 194

LUBRICANT FOR HIGH BEARING PBESSURES -Arnold J. Morway, New York, N. Y., assignor to Standard Oil Development Company, a corporation of Delaware Application November .21, 1933, Serial No. 698,988

No Drawing.

" e 6 Claims. (01. av-9) The present invention relatesto improved lubricants especially leaded lubricants'of the type adapted to withstand extremely high bearing pressures. The invention will be fully understood from the following description.

During the last several years the need for efflcient lubricants adapted to withstand extreme bearing pressures has become more acute and among the various types proposed the leaded 10 compounds have found a definite place, especially for use in automotive transmissions or other power transmitting devices-where steel bearing members are in contact under high pressures of the order of 300,000 pounds per square inch or higher.

Leaded compounds had been previously proposed and it has been found desirable to include sulfur-containing materials in these compositions but there has been little uniformity among the compositions produced and great variation in the quality of the products.- This has been due not only to the different forms in which the lead is present, butalso to the different base stocks, some of which contained sulfur in different proportions. While it has been the general opinion that sulfur is desirable in such compositions, there was little exact knowledge as to the reason therefor and its" actual effect.

It has'now been found that all sulfur comsulfur compounds are of no value whatever others are better, for example, satisfactory at," low speeds, but that to exploit the full capabilities of the leaded compounds the sulfur must not only obtained which are capable of carrying-the'highest required loads under high speeds nowmeces-g o sary for automotive equipment, especially hypoid gears. Y Thegpresent investigation of leaded sulfur compounds has brought out the fact that to be most effective the sulfur present must be in a reactive form. In the following description the type of sulfur compound has been described generally as corrosive. This does not mean that it has objectionable properties when stored in metal containers or on machine parts and the like, but the term is used to designate the various' types of sulfur compounds which will discolor a bright copper strip when in contact therepounds are not equally effective, in factsome be of a particular type but likewise-the lead-and sulfur must be in particular relative proportions. In this manner extremely valuable products are.

sive sulfur present should ordinarily be above .2% and,generally from .3 to 1.5% of the total composition for most purposes and theamount of lead would be suflicient to form lead sulphide with the corrosive sulfur present. For economy, it is preferred not to have an excess oflead, but

if present it is not harmful.

These specific-proportions are of great importance in producing compounds which will withstand load at high speeds while maintaining low friction and consequently low heat evolution. Under these conditions the bearing materials will be maintained in good condition without scratching or scoring. For example, if the sulfur is in a non-corrosive form or if the amount of corrosive sulfur is substantially below that specified above, the compound will not stand the high bearing pressures. If there be .20 to 1.5 of corrosive sulfur present but insuflicient lead, sometimes the load may be carried but there is extreme fric-.

tion, the temperature rises excessively and the bearing members are found to be discolored, scratched and even deeply scored. In some cases under these conditions the load may not be carried due to the high friction but in any case there is considerable damage done to the bearing members. If the lead-sulfur ratio is properly provided and the lead-sulfur compounds are in sufflcient proportion, the load is easily carried with relatively low friction and the heat development is only moderate. .Thebearing members are found to be in an excellent polished-condition, free'from scratching and scoring.

In making up the present compounds a sourceofumaterial containing corrosive sulfur ,may, ofcourse, be, used; for example, heavy petroleum residues, particularly of the type ob- ,tained from West Texas and other known crudes. These compounds, however, contain not only corrosive but also ineffective or non-corrosive sulfur and it is therefore necessary to ,-carefully determine the amount of corrosive sulfur in order to blend the sulfur bearing compound in proper proportion. This may be doneby' first deter mining the totalsulfur and any standard method, for example, by the Bomb method, described in the report of the Committee D4 of the American Society of Testing Materials, 1928, page 174, and

then repeating the determination on a sample which has been deprived of its corrosive sulfur by reaction with flne iy divided metals such as copper, iron or mercury. The corrosive sulfur ture may be increased and the time will be prov portionately diminished. The sulfur, as will be understood, 'combineswith the metal powder and the second determination of total sulfur by a' such acids.

standard method now reports only the non-corrosive sulfur, that is to say, the amount which is not capable of reacting with the copper. The difference between the two determinations gives the amount of corrosive sulfur and in making up the blends they should be based only on this proportion.

Other materials may be used as the source of corrosive sulfur, for example, elemental sulfur itself or synthetic organic polysulphides, preferably the pentasulphide or higher polysulphides, or sulfurized oils of unknown constitution which may be made by cooking mineral, animal, vegetable or marine oils with elemental sulfur, or they may be made by treatment of these or similar materials with knownsulfurizing agents. Lard oil, pine oils and fish oils produce excellent sulfur-bearing compounds by the above methods but as indicated above, a substantial proportion of the sulfur is almost always in a non-corrosive form and it is again requisite to determine accurately the amount of corrosive sulfur and to use referred to above. It is ordinarily observed that the friction starts out at a low figure, increasing as the number of weights is increased. In the case .of the preferred compounds the frictional value increases on a smooth .curve reaching a maximum as the-(last) fifteenth weight is added.

The effectiveness of the lubricant, in cases where all 15 weights are carried, is indicated by the value of the final friction. In some instances where an improper ratio of lead to sulfur is used, it will be observed that the friction does not increase smoothly but increases suddenly as the load is increased by the addition of a weight. In the tables the time of the sudden increasing load is indicated by noting the number-of the weight which caused the sudden increase in friction. It will be appreciated, as indicated above, that a smooth curve is desirable without any sudden increase of this type especially before the last weight is added. The temperature of the oil under test is likewise indicated and the condition of the pinis also described at the end of the this as a basis for the subsequent blending. tests.

Percent sulfur Almen test 'Ratir; cors d ros ya u an Concentrations of E. P. material T t 1 Corn} t d weights IP95! t 1 P (if ltrinal oil a 0 ea ric- 1011a In con 1 1011 em er- Swe named tion inature crease 0.0% lead oleate, 10% sul. lard oil 1. 85 '0. 356 15 52 7 Poor (scratched) 95 5.0% lead oleate, 10.0% sul. lard oil 1. 85 0. 356 1:4 15 58 13 Fair (scratched) 85 10.0% lead oleate, 10.0% sul. lard oil. 1. 85 0. 356 1:8 15 48 15 Good (faintly scratched 70 20.0% lead oleate, 10.0% sul. lard oil 1.85 0. 356 1:16 15 27 Excellent (polishe 62 0.0% lead naphthenate, 5.0% thlopinol. 1.3 0. 15 60 5 Poor (scratched) 96 5.0% lead naphthenate, 5.0% thiopinol. l. 3 0. 5 1:3 15 .43 7 do 90 10.0% lead naphthenate, 5.0% thiopmol l. 3 0.5 1:6 15 40 15 Very good 65 10.0% lead naphthenate, 10.0% th1opinol 2. 6 1. 0' 1:3 15 60 7 Poor (scratched) 88 0.0% lead oleate, 0.4% free sulfur..." 0.6 0. 4 15 65 5 Poor (gouged) 90 5. lead oleate, 0.4% free suliur 0. 6 0. 4 1:3. 5 15 60 7 Fair (scratched) 85 10.0% lead oleate, 0.4% free sulfur 0. 0 0 4 1:8 15 28 Excellent (polished).. 60

The lead compound may be added in any suitably soluble form, for example, as an oleate, naphthenate or sulfonate or as a mixture of any of these substances or as double salts of two of Acids derived by the oxidation of paraffin or other hydrocarbon waxes may also be used, and as indicated above the sulfur and lead should be in proportions of approximately 1 to 6 or 7 by weight in order to have the substance in stoichiometrical ratio to form lead sulflde, but an excess of lead may be present.

The following tests are given to indicate the nature of the present improved compounds and their improved operation. The tests are made on the Almen testing machine which has been described and illustrated in the National Petroleum News of November 16, 1932. In all tests the same base oil is used in order to make them comparable. The base oil has the following characteristics:

Gravity 19.6 Vis. at 100 F 2371 Vis. at 210 F 94.8 Flash, F 440 Pour point 10 Per cent total siilfur .29 Per cent corrosive sulfur None In each of the series tests below a specific sulfur containing material is used and data are presented to indicate both the total and the corrosive sulfur content. The amount of leadin its soluble form is also indicated, together with the ratio of lead to corrosive sulfur. The load carried in the test is indicated by the number of weights in accordance with the Almen method Ingredients of various quality may be used 1) the manufacture of these products and as might be expected the properties of the final compound will differ somewhat depending on the grade or class of the different ingredients and the care of manufacture, but where a proper regulation of the relative amounts of lead and sulfur are made in accordance with the present invention, it will be found that a marked improvement in the compound in respect to load-carrying and frictional characteristics, is obtained.

It will be understood that the invention is not to be limited to any theory of the effect of either the sulfur or the lead. It is true that the most effective quantity of these ingredients is the ratio to form lead sulphide but lead sulphide itself is of little or no value. If it is formed during the use of the oil, it is quite different from the addition of preformed sulphide and by the statementthat such ingredients are in ratio to form lead sulphide is-intended to merely cover the ratio in which the ingredients are used and not to infer a reaction of this or of any other type.

The invention is not to be limited only to the following claims in which it is desired to claim all novelty inherent in the invention.

I claim:

1. An improved lubricant of the extreme pressure type, comprising a heavy hydrocarbon base oil containing about 0.20 to 1.5% of corrosive sulfur and a soluble lead compound in proportion such as to combine to form lead sulfide with substantially no excess of either constituent, the corrosive sulfur being uncombin'ed with lead.

2. An improved lubricant of the extreme presaacaacs such as to combine with the corrosive sulfur to sure type, comprising a heavy hydrocarbon base oil containing about 0.3 to 1.5% of corrosive sulfur and a soluble lead compound in proportion such as to form lead sulfide with substantially no excess of either constituent, the corrosive sulfur being uncombined with lead. 3. An improved lubricating oil of the extreme pressure type, comprising a petroleum oil base together with corrosive sulfur in excess of 0.2% and in the form of one of the following class, free sulfur, sulfurized mineral, .anim'al, vegetable and marine oi1s,and a soluble lead compound selected from the class of oleates, naphthenates, sulfonates and soaps of acid produced by the oxidation of paraffin wax and present in proportion such as to combine with the corrosive sulfur to form lead sulfide with substantially no excess of either constituent, the corrosive sulfur being uncombined with lead.

'4. An improved lubricating composition of the extreme pressure type, comprising as petroleum 1 oil having a viscosity in excess of 100 seconds Saybolt at 210 F. and corrosive sulfur in excess of 0.30% together with lead .oleate in proportion form lead sulfide with substantially noexcess of either constituent, the corrosive sulfur being uncombinedwith lead.

5. An improved-lubricating composition of the extreme pressure type, comprising a petroleum oil having a viscosity in excess of 100 seconds Saybolt at 210 F. and corrosive sulfur in excess of 0.30% together with lead. naphthenate in proportion such as to combine with the corrosive sulfur to form lead sulfide with substantially no excess of either constituent, the corrosive sulfur being unco'mbined with lead. g

6. An improved lubricating composition of the extreme pressure type, comprhing-a petroleum oil having a'viscosity in excess of 1 100 seconds Saybolt at 210 1''. and corrosive sulfur in excess of 0.30% together with lead sulfonate in proportion such as to combine with the corrosive sulfur to form lead sulfide with substantially no excess of either constituent, the corrosive sulfur being uncombined with lead.

J. )ORWAY. 

